Battery powered devices, such as laptop computers, generally use rechargeable batteries so that the batteries can be periodically connected to a source of charging current (e.g., an AC adapter) to recharge the batteries to their full operational capacity. Typically, it is up to the user of such a laptop computer to determine when it is time to recharge the batteries either by monitoring the amount of time the computer has been used or by waiting until the computer stops operating. Many users carry spare batteries to allow the computer to continue to be used when a set of batteries becomes discharged. Often a laptop computer is operated with the batteries only when a source of AC power is not readily available. Thus, frequently the rechargeable batteries are not fully discharged between charging operations. In certain types of batteries, such as nickel-cadmium (NiCad) batteries, it is preferable to occasionally discharge the batteries fully so as to prevent a so-called memory effect problem. Basically, a battery having a four-hour charge capacity, for example, that is only used for one hour, for example, may become a one-hour battery unless it is occasionally fully discharged.
It can be understood that the monitoring of rechargeable batteries by a computer user is generally haphazard at best. Thus, many users frequently find themselves with batteries that do not provide the rated time between charges. Furthermore, a user typically does not know how much time is remaining on the current charge in the batteries when preparing to use the computer without connection to AC power. Software has been developed to reduce this problem. For example, BATTERY WATCH.TM. Release II from Traveling Software of Bothell, Wash., is a terminate and stay resident (TSR) software program that runs in the background on a laptop computer and monitors the operation of the laptop computer to keep track of the amount of time left on the current charge. It performs this function by periodically (e.g., every 3.8 seconds) checking to see which of the hardware components (e.g., floppy disk drive, hard disk drive, display, etc.) are in operation, calculating the amount of power consumed by the operating components and calculating approximately how much charge is remaining in the batteries. When the batteries are recharged, a function key can be activated to inform the software so that the calculations begin again with a full charge. The software operates with different parameters based upon the power consumptions of the components in laptop computers from various manufacturers.
Although software battery monitoring programs are a benefit to many users, such programs still require extensive user interaction to inform the software when the batteries have been recharged and to respond to prompts from the software to connect the computer to a charger when the batteries are approaching the limit of the current charge.